It has been long been considered desirable to integrate photovoltaic (or PV) devices and systems into commercial and residential buildings. To date, however, such systems have been generally limited to conventional roof-top based systems which have limited photovoltaic capability and little aesthetic appeal. Conventional roof-top based systems are limited in photovoltaic capability because, among other reasons, the modules which make up these conventional systems are connected in series which effectively lowers the productivity of the entire system to that of the least productive of the modules. Conventional roof-top based systems also depend upon racking systems which do not afford a practical method to integrate photovoltaic elements into a vertical building face in an attractive and safe manner. Shading by building elements, equipment, and other constraints severely limit the area available for PV deployment.
Clearly it would be desirable to incorporate PV devices in a larger area of a building structure, and in a more visually appealing fashion. In a recent attempt at such an endeavor, a building in New York City incorporated PV elements in vertical façade assemblies that were actually physically separate from the main structure, and configured as artistic elements. The project was in fact a failure due to the inability of the system designer to overcome regulatory restrictions on the incorporation of electrical elements into this type of structure. Thus, while the panels are still attached to the side of the building, they have not been utilized to generate useful PV power.
“Unitized” curtain wall systems are those which can be preassembled and glazed as units (i.e., the glass or other surface material installed) off site and progressively installed section by section on a building. One advantage of the unitized curtain wall approach is that the labor is performed in an off site, controlled, manufacturing environment. Unitized systems are suitable for mid to large projects, i.e. high-rise buildings (four stories or more), those with significant repetition of their components, and/or projects in locations that have higher seismic design requirements. Frame units for unitized curtain walls are typically configured as one module (glazing or glass unit) wide by one story in height. These pre-glazed frames are typically placed on bunks consisting of about 6 units each and hoisted by a tower crane to their respective floors where they are installed, often by utilizing a small mobile hoist from the floor above.
The unitized curtain wall systems also typically include a pressure equalized rain screen, which counteracts the forces that cause water infiltration, such as surface tension, capillary action, gravity, kinetic energy, and pressure differential. Unitized curtain wall systems are in wide spread use and gaining commercial popularity across for the country because of their ease of integration, reasonable cost, schedule-friendly capabilities and aesthetic beauty and high performance.
Photovoltaic modular panels have been integrated into curtain wall glass for building integrated photovoltaics, as seen in U.S. Publication Serial No. 2008/0163918 incorporated by reference herein. Nonetheless the design described is optimized only for amorphous type solar cells, and is not conducive to ease of construction because it is not configured for efficient inter-modular connection. Nor does such design compensate for shading, a problem that severely impairs the performance of conventional series-connected solar panels particularly in articulated applications like building enclosures. As is well known, in conventional PV approaches shading degrades the performance and power output (or yield) of the shaded module or unit. When shading falls on one or more of the conventional series-connected solar panels, the series connected modules degrade in overall performance to that of the lowest yield in the string. Finally the prior art also fails to address the lack of overall Underwriters Laboratory certification or UL approval. UL certification of the framing system is an essential element to enable PV projects to be approved under applicable building and safety regulations, and thus is a key element to enable widespread adoption. Many commercially available modules are UL Approved to UL 1703, but no framing systems related to Building Integrated Photovoltaics (UL Category QHZQ) are commercially available today
WO 2006/123335 incorporated by reference herein suffers from similar deficiencies, in that inter-module connections (in particular those between each individual solar module and those adjacent left and right) are depicted in great detail. However, this system is connected in series, without individual module management. In addition, the array construction method lacks inter-module conduits or passages suitable for routing wiring. Moreover, the modules are connected to each other only in a lateral (left and right) fashion; there is no teaching of vertical connection. For this reason any vertical connections must be accommodated through additional structures, such as tracks, tubes or strips that are not integrated into the curtain wall framing members. U.S. Pat. No. 6,646,196 incorporated by reference herein shows a similar set up, and suffers similar deficiencies. These additional runs add cost and complexity to installation, reduce operational efficiency, raise maintenance costs and complexity, and potentially increase susceptibility to failure.